1. Field of the Invention
This application relates to the fields of image based optical measurement technology, videometrics measurement, and computer vision, in particular, a folding optical path transfer videometrics method for measuring the three-dimensional position, attitude, and their change of non-intervisible objects.
2. Description of the Related Art
Videometrics finds wide application in many fields thanks to its high precision, non-contact, and low cost. However, common videometrics techniques are able to measure only the relative position and attitude of intervisible objects, and they generally become useless when it comes to the measurement of relative position and attitude of non-intervisible objects which widely exist in practical constructions. In constructions and geodetic surveying and mapping, non-intervisible points can be surveyed by setting up middle control points on the obstacles or by avoiding obstacles via relaying of multiple stations when GPS or total stations are used. However, they can determine only the position of the point to be measured but fails to give the three-dimensional position or attitude results of the target. To be even worse, the station setting by those methods are over-complicated, plus real-time measurement is hard to realize when dynamic problems are concerned.
In real constructions, especially large-scale constructions, there are needs for the measurement of the position, attitude, and their change of non-intervisible objects. For example, ship deformations of large vessels take place by the reason of wave impact, temperature differences, load changes, aging, and battle damages, etc., and there is need to measure those deformations; Ship deformation causes changes in the attitude angles of shipboard armament relative to the ship measurement reference, while an intervisible optical path is rare between the measurement reference and the armament to be measured due to the complexity of ship structure, which makes it difficult to precisely align the attitude angle of the armament to the measurement reference. In the construction of tunnel and subways, measuring and monitoring the deformation of the cross section and wall rock are often troubled by short intervisible distance due to the limited tunnel space and the disturbance of ventilation and construction devices. In a word, the lack of an intervisible optical path between the measuring target and the measurement reference in practical constructions denies the application of the conventional videometrics technologies.